1. Field of the Invention
The present invention relates to switch mechanisms for use in electric power tools, such as blowers, for controlling the rotational speed of the tool motors. More particularly, the present invention relates to such a switch mechanism which includes a speed change switch having a plunger and a trigger switch for pushing in the plunger.
2. Description of the Related Art
A typical blower is provided with a switch mechanism which includes a speed change switch having a plunger and a trigger switch for pushing in the plunger. Such a speed change switch is generally accommodated in the handle of the blower. The switch mechanism regulates the rotational speed of the tool motor according to the displacement of the plunger as the trigger switch is pulled in. The Applicant disclosed in Japan Published Unexamined Patent Application No. 6-254779 one such switch mechanism which includes a trigger switch and a regulating member, such as a speed change thumb-screw, mounted on the housing of the tool. The speed change thumb-screw includes a semicircular cam eccentrically mounted on the screw's shaft. When pulled protrusions on the trigger switch are brought into contact with the cam, thus limiting the movement of the trigger switch. Since the semicircular cam of the thumb-screw is eccentrically mounted on the screw's shaft, the user of the tool can readily adjust the maximum amount by which the trigger switch is pulled in by turning the thumb-screw.
While this switch mechanism achieves its intended objective, it is not free from certain problems and inconveniences. For example, as the trigger switch is located away from the speed change thumb-screw, when the user grips the handle, for example, with his right hand and pulls the trigger switch with the index finger, no other finger of the hand reaches the thumb-screw. As the user cannot operate the two elements simultaneously with one hands the left hand is needed to adjust the speed change thumb-screw. However, as a blower is often operated by one hand to direct airflow to various objects held by the other hand, operation of this switch mechanism requires the user to interrupt the work in order to adjust the setting of the thumb-screw to change the airflow. This reduces the ease of use of the tool and affects work efficiency.